Kernel builds with gcc
The recommended compiler for building Linux 2.4 is gcc 2.95. New compilers upto gcc 3.3 have been used successfully to build the kernel however with gcc 3.4 there may be problems when certain configurations. With Linux 2.4 being in deep freeze mode we generally don't intend to fix such problems but rather recommend to use an older compiler for the kernel.
The latest "official" GCC 2 is version 2.95.3. The GCC 2.96 is unofficial massively patched version. It provides more efficient optimization with -O2, more strict syntax checkhing and supports more recent C++ standarts. Unfortuntely, C++ ABI is not compatible with "official" 2.95.3 nor 3.0.
Kernels upto 2.6.15 require a gcc 2.95..4.0. Gcc 4.1 is still considered experimental at this point so not recommended where reliability matters. Kernels newer than 2.6.15 require at least gcc 3.2. See a related article on Kerneltrap.